Fender DRRI and SRRI: Not enough headroom

[stratomaster]

Any other ideas as to why I can't play bass notes at higher volumes (past 2.5 on volume knob) without the amp distorting?

[txstrat]

Any other ideas as to why I can't play bass notes at higher volumes (past 2.5 on volume knob) without the amp distorting?

Have you tried to put the tremolo pot back in the circuit? Or roll back any other mods?
I mean putting it back to stock to find out whether it's related to the mods you did.
From there you can start to do one mod at a time...

[stratomaster]

Yes, I have tried going back to stock (both mods are easily reversed, with a switch and by putting the tube back in). I responded earlier with PI plate voltages, but I guess my post got buried somewhere on the 1st page.

Going back to stock doesn't really help. If there in an increase in headroom, it's hard to tell. Assuming the mods aren't the culprit, what should I look for?

[txstrat]

Did you try a different guitar?

[stratomaster]

Sure did. 3 in total. It's the worst with a humbucker equipped guitar (presumably due to the hotter signal).

[txstrat]

What I was aiming at is, that if it happens in both amps, when back to stock, I don't think it has to do with the amps rather than something else. Cables, effects, etc...
Generally an ugly distortion could be caused by failing coupliong caps, or failing plate resistors as well as some other things. Did you follow the hints on the geofex tube amp debugging page?

[stratomaster]

I've used different cables and different guitars. Both with and without effects. It's not like the amps are full blown distorted all the time, which is kind of the vibe I got from reading R.G.'s tube amp debugging page. They just flub out on the lower notes at stage volumes.

[txstrat]

The switch you are talking about (to undo the mod), was it there in the first place?
It might be a place to look for trouble. Just a thought.

[stratomaster]

I'm using the dummy ground switch that was put in the DRRI earlier models. And I'm using a switched pot in the SRRI.

[ajeffcote]

If it is only the low notes giving you the problem,turn the bass pot all the way off!!OK,maybe that is a little drastic,but if you are turning that pot up a lot.........The DRRI has a bassy voice.And the SRRI is about the same circuit,I think.I'm just thinking out loud here.
What about the speakers you are using?The Jensen that came in my DRRI exhibits a lot of farting at higher volumes,and with the bass turned up the sound gets mushy also,and sounds like it is distorted.
When you crank it up,sometimes less is more.

[stratomaster]

If it is only the low notes giving you the problem,turn the bass pot all the way off!!OK,maybe that is a little drastic,but if you are turning that pot up a lot.........The DRRI has a bassy voice.And the SRRI is about the same circuit,I think.I'm just thinking out loud here.
What about the speakers you are using?The Jensen that came in my DRRI exhibits a lot of farting at higher volumes,and with the bass turned up the sound gets mushy also,and sounds like it is distorted.
When you crank it up,sometimes less is more.

There are a few different things going on with the volume coming up, (and I do turn the bass down as the volume comes up--its a trick I learned with a little crate practice amp I had about 8 years ago) the sound gets mushy and the low notes are distorting moreso than the high notes. There is still distortion present on high notes as well, but the mush mixed with the distortion make for a very nasty sound.

These are all good tips you all are giving me, but there is no reason why I shouldn't be able to get clean sounds out of these amps at around 3 on the volume knob no matter what the EQ is set at.